Method of assembly of a loud speaker



Aug. 23, 1960 C. A. PERRY METHOD OF ASSEMBLY OF A LOUD SPEAKER OriginalFiled Oct. 1, 1956 INVENTOR. CHARLES A. PERRY BY Arron/v05 ted StatesPatent 915 2,949,663 Patented Aug. 23, 1960 2,949,663 WTHOD F ASSEMBLYOF LOUD SPEAKER harles A. Perry, Cleveland, Ohio, assignor to The RolaCompany Inc., Cleveland, Ohio, a corporation of Ohio Originalapplication Oct. 1, 1956, Ser. No. 613,187. Divided and this applicationDec. 9, 1957, Ser. N0.

1 Claim. (Cl. 29-45559) supporting structure in the form of a housingand a mag-- netic field structure for energizing the diaphragm voicecoil. In a permanent magnet type loud speaker, the field structure mayinclude a yoke, a magnet mounted thereon, a pole ti a front plate andsome arrangement for protecting the air gap from the accumulation offoreign particles. An inherent problem in the assembly of permanentmagnet type loud speakers is the excessive labor and cost involved inthe multiple handling of the component parts. There are also additionalsupplemental operations required to adjust the magnet and to insure thatthe diaphragm voice coil is properly centered in the air gap formed bythe field structure.

It is a principal object of this invention to provide a simplified andimproved method for assembling and mounting a permanent magnet fieldstructure on the diaphragm housing of a loud speaker without the needfor cement, soldering or threaded fasteners of any kind.

A further object of this invention relates to the provision of animproved method of assembling and mounting a permanent magnet fieldstructure-on the-diaphragm housing of a loudspeaker which automaticallyand per manently centers the pole tip in the air gap during suchassembly and mounting.

Briefly, the foregoing objectives are attained in accordance with thisinvention by providing a U-shaped yoke with projecting guides that areadapted-to pass through properly located apertures in a front platewhich are in turn aligned with similarly located apertures on adiaphragm supporting housing. The diaphragm housing and front plateinclude central bores for receiving the voice coil which are adapted tobe axially aligned by virtue of the alignment of the foregoing apertureson the projecting guides. The front plate has projecting pins spacedcircumferentially about the central bore on its rear face which areadapted to engage similarly located apertures on a mating flange of amagnet centering member. The centering member is made of non-magneticresiliently flexible material and is cup-shaped with a depressed centralportion that is adapted to overlie the central bore in the front platewhen mounted thereon. The front plate and centering member are firstassembled as a sub-assembly by staking them together and at the sametime piercing a bore through the depressed portion of the centeringmember which will be concentric with the bore in the front plate so thata core tip projecting through the centering member bore will beconcentric with the front plate bore. This is accomplished by pilotingthe piercing operation through the bore in the front plate. A permanentmagnet is supported within the yoke with its projected axis extendingthrough the concentric bores and a pole tip is mounted on the projectedextremity of the magnet and secured in centered position within theconcentric bores by means of the non-magnetic centering member. Theyoke, magnet, pole tip and the centering member and front platesub-assembly are then assembled on the diaphragm housing with the yokeguides extending through the apertures in the front plate and diaphragmhousing. Pressure is then applied to deform the projecting extremitiesof the guides and thereby fasten the component parts together. The depthof the depressed portion of the centering member is such that thepressure will collapse the depressed portion slightly and the resiliencyof the centering member will hold the pole tip in centered relationwithin the front plate bore.

In the drawings: Fig. 1 is a side elevation of a loud speaker having thefield structure partially cut away to illustrate the interior;

Fig. 2 is an exploded perspective view of the subassembly of a frontplate and core tip dust cup at an intermediate stage of assembly;

Fig. 3 is an exploded perspective view of the field structure inrelation to the diaphragm housing; and

Fig. 4 is an enlarged sectional view of the centering portion of theassembly.

Referring now more particularly to Figs. 1 and 3 of the drawings, thereis shown a preferred form of the loud speaker assembly of this inventionhaving a permanent magnetic field structure which includes a yoke,indicated generally at 10, which is formed from a metal blank bent inthe form of an open U-frame having a back plate 11 and sides 12 and 13.The field structure also includes a magnet 15, and a pole tip 16 and asubassembly which includes a front plate 18 and a centering member 19which is fastened thereto by projecting nubbins 32.

The sides 12 and 13 of the yoke 10 are provided with outwardlyprojecting tangs 21 and 22 at their extremities so devised as to projectthrough spaced apertures 23 and 24 respectively in the front plate 18and subsequently through similarly located apertures 26 and 27 in therear of the diaphragm housing 20. The apertures in the front plate anddiaphragm housing are located so that when they are aligned with eachother along the tangs 21 and 22, the housing 17 will be aligned axiallywith a central bore 28 in the front plate 18. The magnet 15 is supportedon the back plate 11 of the yoke and in turn is extended axially by thepole tip 16 which extends through axially aligned bores 29, 28 and 17 inthe centering member 19, the front plate 18 and diaphragm housing 20 insuch manner as to define a concentric air gap surrounding the pole tip,which is adapted to receive in centered relation a voice coil 30 carriedby the throat of the diaphragm. 7

Referring now more particularly to Fig. 2 of the draw ings, the frontplate 18 and centering member 19 are shown disassembled in the explodedview to expose the projecting nubbins 32 on the rear face of the frontplate, which are spaced from each other circumferentially about thecentral bore 28. The centering member 19 is composed of a resilientlyflexible and non-magnetic cupshaped member having a planular flangedportion 33 with apertures 34 through the respective corners forreceiving the nubbin-like projections 32 on the rear face of the frontplate. The central portion 35 of the centering member is depressed toform a dust cup which is adapted when assembled to surround the pole tip16. In the preferred form shown, the centering member is staked to thefront plate 18 and the depressed dust cup 3 portion 35 is pierced byasuitable die which is piloted through the bore 28 in the front plate 18to make the bore 29 concentric with the bore 28. In assembly the bore29, which is of substantially the same or slightly greater diameter thanthat of the pole tip 16, automatically guides the pole tip into centeredrelationship, is'

maintained fixed without fear of distortion from bumps that normallyoccur in the rough handling incident to the packing and shipment of loudspeakers from the place of production to the set manufacturer andultimate user, as will be hereinafter more fully described.

The form and structure of the limited number of parts of the loudspeaker field structure is such as to simplify the assembly and reducethe amount of handling necessary in producing the loud speaker. Themethod of assembly contemplates that the yoke is first placed open endup with its back plate resting on the stationary head of a press. Themagnet 15 is then located in a slight recess 36 which is provided on theinner face of the back plate 11 to insure that the magnet will not slideout of the yoke. The pole tip 16, which is provided with a flange 37 onone extremity, is inserted into the bore of the centering member 19, andthe pole tip and sub-assembly of the front plate 18 and centering member'19 are then placed as a unit upon the yoke with the tangs 21 and 22projecting through apertures 23 and 24 in the front plate 18. Thisoperates to position the magnet and pole tip 16 in centered alignmentand at the same time brings the flanged end 37 of the pole tip intoabutting engagement against the adjacent end of the magnet.

Thereafter, the diaphragm housing is placed over the front plate 18 withthe apertures 26 and 27 in registration with the apertures 23 and 24, atwhich time the tangs 21 and 22 project through the apertures. While. theassembly is so held on the stationary head of the press, the movablehead of the press is brought down so as to swage the tangs 21 and 22against the front face of the diaphragm housing 20. The depth of thecentral depressed portion 35 of the centering; member 19 is such thatthe press initially collapses the portion 35 slightly against the flange37 and causes the wall of the portion 35 to deform inwardly to insure atightly centered assembly of the component parts. The position of theportion 35 before and after the application of pressure by the press isillustrated in Fig. 4 of the drawings, wherein the broken linerepresents the position before deformation and the full line representsthe position after deformation. Further pressure from the pressfollowing the collapsing of the central portion 35 swages the tangs 21and 22 against the front face of the diaphragm housing to permanentlysecure the component parts together in centered relation.

It will be readily apparent that the automatic and permanent centeringwhich results from the construction and method of assembly hereinbeforedescribed-eliminates the necessity for the use of centering gauges andalso. reduces the number of parts and major handling operations as wellas those additional supplemental operations ordinarily required tocenter the core tip and voice coil within the air gap.

' ing the diaphragm housing on I have shown and described what Iconsider to be the preferred embodiment of my invention, and it will beobvious to those skilled in the art that other changes and modificationsmay be made both in the construction and in the method of assembly ofthe loud speaker without departing from the scope of my invention asdefined by the appended claim:

I claim:

In aloud speaker assembly having a diaphragm housing with a centralvoice coil opening and with apertures on either side thereof and havinga magnetic field structure including a U-shaped yoke having side plateseach with a projection, extending therefrom and having a back platejoining said side plates, said back plate having a centered depressedportion adapted to receive a magnet, and a magnet and a flanged pole.tip therefor, a front plate for the yoke having a central bore adaptedto surround the pole tip and form a voice coil air gap and havingapertures on either side thereof for receiving the side plateprojections therethrough, and a non-magnetic re siliently flexible, poletip centering member having a depressed portion adapted to. have formedtherein a central bore of substantially the same diameter as the poletip, the method of assembly consisting of, fixing the centering memberover the bore in the front plate by deforming coacting portions of theplate. and centering members, then piercing to, form a central borethrough the depressed portion of the centering member in concentricrelation to the front plate bore, placing and resiliently retaining thepole tip in the centering member bore thus formed with itsv flangedextremity disposed external thereto, placing the yoke back plate on ahorizontal surface, placing the magnet on the back plate of the yoke inthe centered depressed portion thereof with its axis parallel to andbetween the side plates, then mounting the front plate, the centeringmember and the pole tip as a subassembly on the yoke side plates bypassing the side plate projections through the front plate apertures,then mountthe front plate with the yoke side. plate projections passingthrough the housing apertures, then axially pressing the housing againstthe front plate. and yoke side plates to compress the depressed portionof the centering member against the pole tip flange and magnet, andthereafter deforming the side plate projections to secure the loudspeaker assembly together with the pole tip accurately centered withinthe air p- References Cited in the file of this patent UNITED STATESPATENTS 2,404,456 Pierce July 23, 1946 2,501,031 Cunningham Mar. 21,1950 12,663,270. Friedly. Dec. 22, 1953 2,666,980 Russell Jan. 26, 19542,697,873 Cook Dec. 28, 1954 FOREIGN PATENTS 521,809 Great Britain May31, 1940

